As some people have problems to adjust some parts of the dialogs, and in fact it's some code that it's always being adjusted and reused, I've created this plugin that allows to remove dialog fields or change their default values by using some configuration values.
More info in this blog post about configuring dialogs , this one about placeholder and hiding fields.
Licensed under the terms of any of the following licenses at your choice: GPL, LGPL and MPL.
ConfigHelper plugin page
1. Extract the contents of the file into the "plugins" folder of CKEditor.
2. In the CKEditor configuration file (config.js) add the following code:
config.extraPlugins = 'confighelper';
3. Set the fields that you want to remove or change as explained in the included doc.